1. The Field of the Invention
The present invention relates to systems for attaching flexible catheters to medical devices.
2. Background Art
Catheters are used extensively in the medical field to facilitate the performance of recurrent therapeutic tasks inside the body of patients.
For example, using only a relatively small incision, a catheter can be implanted in the body of a patient and used to deliver fluid directly to a predetermined location, either within the cardiovascular system, the peritoneal cavity, or some organ, such as the stomach, the heart, the liver, the brain, or the reproductive tract. Alternatively or in addition thereto, such implanted catheters can be used to periodically sample from these locations, to drain fluids to relieve pressure, to withdraw fluids for extracorporeal processing on an ongoing basis, or to monitor internal body conditions, such as pressure, temperature, or fluid flow rates.
Catheters are, however, fabricated in various structural configurations, depending upon the intended use for each.
A common catheter design used in performing many of the procedures mentioned above includes an elongated, flexible cylindrical catheter body having a fluid flow passageway or a lumen extending along the interior of that catheter body. During use, an end of the catheter referred to as the distal end is inserted into the body of the patient through an incision or a body orifice and then entered into a body cavity or internal passageway, such as a blood vessel in the cardiovascular system. The distal end of the catheter is advanced within the body cavity or along the internal passageway until the distal end is located at a desired predetermined location for conducting an intended therapeutic activity. Fluid containing medication, nutrients, or cleansing agents can then be introduced through the lumen of the catheter and delivered at the predetermined location through the distal end of the catheter.
The end of such a catheter opposite the distal end is referred to as the proximal end. Once the distal end of a catheter has been implanted at a predetermined location as described above, the proximal end must be attached to the type of medical device that is appropriate to the specific task and manner of use to which the implanted catheter is to be applied. On some occasions the distal end of the catheter with the attached medical device remains outside the body of the patient. In other situations both are implanted subcutaneously in the body of the patient.
For example, if the proximal end of an implanted catheter is to remain outside the body of the patient, the proximal end of the catheter is frequently attached to a catheter termination device that facilitates access to the lumen by a hypodermic needle. Commonly, such catheter termination devices also function to close the proximal end of the catheter when the infusion or withdrawal of fluid is not taking place. In some circumstances the proximal end of an implanted catheter may need to be coupled to tubing that allows the proximal end of the catheter to in turn be fluid coupled to sizable medical devices that must remain outside the body of the patient. In such circumstances the catheter termination device to which the proximal end of the catheter is coupled is ideally selectively and non-destructively couplable with tubing, but the catheter termination device is also provided with the capacity to close the proximal end of the associated catheter whenever such tubing is detached.
On occasion the proximal end of the catheter is attached to one side of a fluid flow accommodating structure that has on the other side structures appropriate for coupling to yet another catheter. This may be done to increase the length of a catheter that is already implanted, or to splice the broken proximal end of an implanted catheter.
In some instances, the proximal end of an implanted catheter will be attached to an access device that is itself also implantable in the body of a patient. Then the entirety of the catheter with the access device attached thereto is embedded at appropriate locations in the tissue of the patient with the distal end of the catheter disposed at the predetermined location at which therapeutic activity is to be effected. Under such circumstances, medication is then delivered to the lumen of the catheter, or withdrawn therefrom, utilizing a hypodermic needle that penetrates the skin of the patient at the implantation site of the access structure and effects a fluid coupling with that access structure.
One problem encountered in attaching the proximal end of a catheter to a given medical device is that catheters are fabricated from a variety of different materials. These materials vary in material properties, such as tensile strength, shear strength, flexibility, and compressibility. Some materials tend to relax over time after being stretched over a rigid structure, a property referred to as creep, while others do not. Some kink more easily than others. Some shear easily in specific directions, while others resist such structural failures.
Silicone and polyurethane are materials used extensively in the medical field in the manufacture of implantable catheters. Silicone and polyurethane each have unique material properties. The use of one material over the other is usually determined by the intended use of the catheter and the conditions in the body to which the catheter will as a result be exposed. Often the selection of a catheter of one material over a catheter of another material is to a large degree merely a function of availability or of the preferences and prior experience of the medical personnel who will use the catheter selected.
The different materials from which catheters can be fabricated results in the availability of catheters having dramatically different material properties.
One area in which different material properties in catheters can have a significant impact is the behavior of the catheter in relation to the catheter attachment structures used to secure the proximal end of a catheter to a medical device. Some types of catheter attachment structures are inappropriate, or even dangerous, when used in connection with catheters made of a particular material. In many cases a specific catheter attachment structure is appropriate, or even safe, only when used with catheters made of a single, specific material.
Catheter attachment structures may cut, tear, or shear catheters of one material, while functioning with absolute safety relative to catheters made of another. One catheter attachment structure may be unable to effect a secure mechanical connection or a fluid tight seal relative to a given catheter material, while performing with adequate safety in relation to another catheter material. One catheter material may be incapable of cooperating effectively with the elements of a given catheter attachment structure, while being ideally suited to doing so with the elements of a different catheter attachment structure.
Thus, if a medical facility intends to permit its personnel to utilize catheters made from a selection of different materials, these facilities must correspondingly purchase and maintain an inventory of corresponding, appropriate catheter attachment structures for each type of catheter material.
Some brands of medical devices are manufactured with components of only a single type of catheter attachment system secured thereto. Thus, the freedom of medical practitioners to select among catheters made of different materials is limited in some cases by the brand of the medical device that is intended to be used in the procedure. Under such circumstances, the freedom to select differing catheter materials is in fact illusory, unless several brands of a given medical device are kept on hand at a medical facility.
The same problem also exists for using different sizes of catheters. That is, at times it is desirable to use a catheter having a larger or smaller size lumen extending therethrough. The size of the lumen affects the flow rate at which a medication can be delivered or a body fluid removed. Medical devices are typically manufactured with catheter attachment systems that can only be used with a catheter having a single defined lumen size. Thus, to enable a medical practitioner to selectively choose a catheter having a defined lumen size and material composition, a medical facility must carry a variety of sizes and brands of medical devices.
This issue is equally as complicated in relation to catheters having more than a single lumen. Dual lumen catheters allow two medications to be delivered simultaneously to a location in the body of a patient. As with single lumen catheters, dual lumen catheters can also be made of different materials and have varying lumen sizes. Thus, medical facilities must also carry selections of varying medical devices that can accommodate different kinds of dual lumen catheters.
In most instances at least one component of each catheter attachment structure is permanently secured to the medical device to which a catheter is to be coupled. Thus, the selection of one catheter attachment system frequently implies the selection of a corresponding medical device. An inventory of differing catheter attachment systems can, therefore, require in reality an inventory of different medical devices.
The purchase of different catheter attachment structures and several brands of a given type of medical device is expensive and requires a commitment of space to store an inventory. Once these costs are assumed, however, the availability of a variety of catheter attachment structures and a plurality of brands of medical devices at a medical facility will afford the medical personnel the freedom to use catheters fabricated from a variety of materials.
The availability of a plurality of types of catheter attachment structures does, however, require close attention to the correct correlation between a catheter and the catheter attachment structure by which it is to be coupled to a medical device. If an inappropriate catheter attachment structure is utilized, the attachment between a catheter and a medical device can leak, or even fail altogether.
Ensuring that a secure mechanical connection and a reliable fluid tight seal is effected between a catheter and a medical device is of utmost importance with regard to assemblies of a catheter and an attached medical device that is to be totally implanted within the body of a patient. In such a situation, an ineffective mechanical coupling or an improper fluid seal can result in major complications and expose a patient to painful, if not fatal, risks.
The failure of the mechanical coupling between an implanted catheter and an implanted medical device can result in one or the other becoming free to migrate throughout the body. Surgical intervention will then be required to locate and remove the loose article. Naturally under such conditions the delivery of medication or the withdrawal of fluid from any predetermined location in the body of the patient is totally frustrated.
Less dramatic, but possibly more insidious, is a catheter attachment with a medical device that is ineffective in producing a reliable fluid seal. Medication will then leak from the implanted assembly at the catheter attachment structure, diverting medication to an improper location. In many cases such misdelivered medication is damaging of tissue about the catheter attachment structure.
Such malfunctions may go undetected for some time, correspondingly resulting in the need for compensatory medical treatments to repair the damage produced. In addition, any failure to deliver medication in at a prescribed rate to a planned predetermined location will undermine the efficacy of a planned course of treatment. Naturally, if leaking is present in the system by which the medication is delivered, the time of the course of treatment will be extended.
Any of the circumstances described above will invariably require the removal of the catheter and the medical devices involved, the replacement of one or both, and then the surgical reimplantation of the entire assembly. Often this must occur at a fresh implantation site, as the original implantation and removal of such devices will have rendered the initial implantation site unusable, at least until a period of healing has passed.
All of these consequences of ineffective catheter attachment unnecessarily add to the duration and to the cost of medical procedures.
Even where an attachment is to be effected to the proximal end of a catheter outside the body of a patient, delay, equipment replacement, and enhanced costs can be anticipated, if a catheter attachment structure is used that is inappropriate to the material of which the associated catheter is made.